Liquid detergent compositions

ABSTRACT

DETERGENT COMPOSITIONS OF LINEAR ALKYLBENZENE SULFONATES CONTAINING A MIXTURE OF SODIUM AND ETHANOLAMINE SALTS OF SAID SULFONATES AND POLYETHYLENE GLYCOL. THE COMPOSITIONS ARE CHARACTERIZED BY HAVING IMPROVED LOW TEMPERATURE STORAGE STABILITY.

United States Patent U.S. Cl. 252-545 4 Claims ABSTRACT OF THEDISCLGSURE Detergent compositions of linear alkylbenzene sulfonatescontaining a mixture of sodium and ethanolamine salts of said sulfonatesand polyethylene glycol. The compositions are characterized by havingimproved low temperature storage stability.

Detergents such as the alkylbenzene sulfonates are commonly marketed inthe form of liquid, aqueous compositions. These liquid detergentcompositions offer the advantage of convenience in consumer use in thecleansing of dishes and fabrics. One of the most commonly employeddetergents in such formulations is sodium alkylbenzene sulfonate whereinthe alkyl substituent is from about 9 to 15 carbon atoms and may beeither branchedchain or linear. In recent years the emphasis onbiodegradable products has resulted in the increasing importance of thelinear type of alkylbenzene sulfonates since the linear orstraight-chain type is readily degraded by microorganisms found insewage. A disadvantage encountered generally in the production ofaqueous solutions of detergents has been the problem of producing liquiddetergent compositions having low clear points, i.e. solutions which donot become turbid or clouded from layers of precipitated matter atrelatively low temperature. Such has been the case with aqueoussolutions of sodium alkylbenzene sulfonates when after storage at lowtemperatures they tend to become cloudy and may thicken to a gellikestat or even undergo a phase separation. While the occurrence of suchphenomena does not adversely alfect the cleansing properties, it doespresent problems with respect to appearance and pourability of thecomposition and is undesirable from a marketing standpoint. It is aparticularly troublesome problem when handling sulfonate solutions inbulk, i.e. transportation in tank cars or storage in unheated tanksespecially in cold weather.

It has been found that in the-case of the branched-chain type of sodiumalkylbenzene sulfonates the problem could be solved by the addition ofcertain modifiers including a lower alkylbenzene sulfonate such as atoluene sulfonate or a glycol such as ethylene glycol. With aqueousformulations of the linear type, however, the problem is considerablymore acute and even with addition of such modifiers the problem stillexists when these modified linear type formulations are stored at lowtemperatures.

It has now been discovered that aqueous liquid compositions of linearalkylbenzene sulfonates can be prepared which have the specificadvantage of remaining clear and fluid even after extended periods ofstorage at low temperatures.

In accordance with the present invention there is prosubstantiallyimproved low temperature stability containmg:

(A) as solutes therein between about 30 and 50% of sodium andethanolamine salts of a mixture containing a major proportion of linearhigher alkylbenzene sulfonates wherein the alkyl constituent is astraight chain hydrocarbon of 9 to 15 carbon atoms, preferably 10 to 13carbon atoms, and a minor proportion of lower alkylbenzene sulfonatescontaining between 1 and 6, preferably 2 to 4 non-aromatic carbon atoms,and

(B) between about 0.5% and 5%, preferably between 1 and 2% of apolyethylene glycol having an average molecular weight of between about200 and 1250, preferably 400800, the higher and lower alkylbenzenesulfonates being present predominantly as sodium salts with asolubilizing amount of monoethanolamine salts thereof. Substantiallyimproved low temperature stability is achieved in compositions whereinthe ratio of monoethanolamine to sodium cations is between about 0.1 and1.0 preferably 0.3 to 0.7.

The higher linear alkylbenzene sulfonates of the present compositionscan be prepared by any one of a number of Well-known methods such assulfonation of the corresponding linear alkylbenzene, for example, byreaction with percent sulfuric acid and neutralization of resultantalkylbenzene sulfonic acid with sodium hydroxide and monoethanolamine.The higher linear alkylbenzenes are commercially available compounds,commonly pre pared by condensation of the partially halogenated productof a normal paraffin of 9 to 15 carbon atoms, or mix tures thereof, withbenzene in the presence of a Friedel- Crafts catalyst such as aluminumchloride. Processes of this type are described in US. Pats. Nos.2,314,255, 2,3 64,- 767 and 2,387,572. Representative of the linearalkyl substituent on the benzene nucleus are such groups as decyl,dodecyl, keryl, pentadecyl, etc. and mixture thereof.

The lower alkylbenzene sulfonates function as solubilizing agents in thecompositions of the present invention. They are employed in amountssufficient to provide a mol ratio from about 4.0 to about 2.5,preferably 3.0 to 3.5, of higher to lower alkylbenzene sulfonate. Thesecompounds are prepared as described above by sulfonating thecorresponding alkylbenzene and neutralizing the resultant sulfonic acidwith sodium hydroxide and ethanolamine. Suitable compounds include thehomologs of benzene sulfonate containing from 1 to 6 non-aromatic carbonatoms, for example the sulfonates of toluene, xylene, cumene, cymene,butylbenzene, amylbenzene, hexylbenzene, butylxylene and the like.Because of its availability, relatively low cost and freedom fromundesirable coloration effects, toluene sulfonate is preferred. Thelower alkylbenzene sulfonate may be added to the composition prior tosulfonation (as the alkylbenzene), or prior to neutralization (as thesulfonic acid) or after neutralization of the higher alkylbenzenesulfonic acid. In the latter case the lower alkylbenzene sulfonate isadded in the form of a mixture of sodium and monoethanolamine saltswherein the mol ratio of monoethanolamine to sodium cations is betweenabout 0.1 and 1.0.

The polyethylene glycols, which also serve as solubilizing agents in thecompositions of the present invention,

are commercially available high molecular weight compositions of thegeneral formula HOCH CH OCH CH OH wherein n is an integer from about 2to about 10. They are commonly prepared by the reaction of ethyleneglycol with varying amounts of ethylene oxide. The polyethylene glycolsare commercially available in a wide range of molecular weights. For thepurpose of the present invention those having an average molecularweight of between about 200 and 1250 have been found most suitable.Thus, they include triethylene glycol, tetraethylene glycol and higherpolyethylene glycols having molecular weights within this range. Theymay be employed in the form of the individual polyglycol or in the formof mixtures such as are obtained commercially by the reaction of aglycol with ethylene oxide. The glycols may be employed in amountsranging from 0.5% to 5%, preferably 1% to 2% of the weight of the finalsolution. The glycols can be incorporated into the detergent solution atany stage of the manufacture thereof subsequent to the formation of thesulfonic acid, and in any order with respect to the other components ofthe solution. An advantageous procedure for the manufacture of thesolution involves carrying out the neutralization of the higheralkylbenzene sulfonic acid in an aqueous medium containing the glycol.

In a preferred method of preparing the compositions of the presentinvention, toluene and a higher linear alkylbenzene are combined in theproportions stated hereinabove and the mixture is sulfonated by reactionwith 100 percent sulfuric acid in a known manner. The reaction mass isthen allowed to settle and a phase separation occurs. The lower layer ofspent sulfonating acid is withdrawn. The upper layer, comprising amixture of higher linear alkylbenzene sulfonic acid and toluene sulfonicacid is charged into a mixture of water and a polyethylene glycol havingan average molecular weight between 200 and 1250. Simultaneously withthe charging of the sulfonic acid mixture to the water-glycol mixture, astream of monoethanol amine is added in sufficient quantity toneutralize the desired amount of the alkylbenzene sulfonic acid mixture.The remaining unreacted sulfonic acid mixture is then neutralized byaddition of aqueous sodium hydroxide.

Various other modifiers such as are commonly employed in detergentcompositions may be added. Such additional modifiers may be present inamounts up to about percent by weight based on the final weight of thedetergent solution. Typical additives which may be employed are sodiumtripolyphosphate which serves as a sequestering agent for iron, sodiumhypochlorite, which functions as a purifying agent (as described in US.Pat. 2,333,830), sodium bisulfite, which serves to decompose anyresidual sodium hypochlorite in the treated solution, and others. Watermay be added to the composition during the preparation or after toprovide the degree of concentration desired. The concentration may varyconsiderably, the usual being between about and percent solids in thefinal aqueous composition.

To further illustrate the present invention and the manner in which itmay be practiced, the following specific examples are set forth. In theexamples, unless otherwise indicated all parts are by weight and alltemperatures are in centigrade degrees.

EXAMPLE 1 Ten parts of toluene was mixed with 90 parts of a linearalkylbenzene consisting predominantly of C -C paraffin hydrocarbonsubstituents and having an average molecular weight of about 241(available commercially as Phillips linear detergent alkylate Type-1,Phillips Petroleum Co.). To the mixture, 146 parts of 100 percentsulfuric acid were added and the reaction mixture was agitated at 55 to58 degrees for about one hour. Next, 29.5 parts of water were added,with cooling to maintain the temperature of the reaction mass below 70degrees. Following the addition of water, the reaction mass was allowedto settle while the temperature was maintained at 65 to 70 degrees. Aphase separation occurred over a period of about one hour and the lowerlayer of spent sulfonating acid was withdrawn. The upper layer ofalkylbenzene sulfonic acids was neutralized in the following manner:Separate streams of the alkylbenzene sulfonic acid and ofmonoethanolamine (12.3 parts) were charged simultaneously to a mixtureof parts of water and 5.6 parts of a commercial polyethylene glycolhaving an average molecular weight of about 400 (Polyglycol E400, DowChemical Co.). Next, 18.5 parts of sodium hydroxide were added (as a 30%aqueous solution) to neutralize the remaining sulfonic acid. Near theend of the neutralization procedure the batch was treated successivelywith the addition of a solution of 1.67 parts of sodium tripolyphosphatein water, 1 part of a 10 percent sodium hypochlorite solution and 0.49parts of sodium bisulfite in water.

The final acidity of the solution was adjusted to a grassgreen color onNitrazine Yellow test paper (a pH of 6.3 to 6.7). Sufificient water wasadded to adjust the total solids content to 41.0 percent. The detergentsolution thus prepared was stored at a temperature of 2 to 4 degrees fora period of several months. The solution remained clear and fluid.

EXAMPLE 2 To a mixture of parts of toluene and 1000 parts of sulfuricacid-washed linear alkylbenzene consisting predominantly of C -Cparaffin hydrocarbons having an average molecular weight of about 241(available commercially as ARLA-4, Atlantic Refining Co.), was added 767parts of 100 percent sulfuric acid and the reaction mixture was agitatedfor about 1 hour at 55 to 58 degrees. Next, 300 parts of water wereadded and the temperature was maintained at 65 to 70 degrees for aboutone hour while the reaction mixture settled and separated intotwolayers. The lower layer comprising spent acid was withdrawn. Theremaining mixture of alkylbenzene sulfonic acids was combined with 340parts of water and 26.7 parts of polyethylene glycol having an averagemolecular weight of 400 (Polyglycol E- 400. Dow Chemical Co.) andneutralized with 28.2 parts of monoethanolamine and 48.7 parts of sodiumhydroxide (as a 30% aqueous solution). To the neutralized mixture wereadded 8.0 parts of sodium tripolyphosphate in 26.8 parts of water, 1.5parts of a 10 percent sodium hypochlorite solution, and 1.9 parts ofsodium bisufite in 5.3 parts of water. Sutficient water was added toadjust the total solids content to 41.0 percent. The detergent solutionthus prepared was stored at a temperature of 2 to 4 degrees for a periodof several months. The solution remained clear and fluid.

EXAMPLE 3 The procedure of Example 1 was repeated except thatmonoethanolamine was omitted and the amount of sodium hydroxide wasincreased accordingly to 25.6 parts to neutralize the acids. Theresultant detergent solution was stored at a temperature of 2-4 degrees.At the end of the third day in storage the solution appeared cloudy andby the end of the fourth day was a gel-like solid.

EXAMPLES 4-11 The procedure of Example 1 was repeated except that theamounts of monoethanolamine and sodium hydroxide were varied as shown inTable 1 below. The solutions, thus prepared, were stored at 2-4 degreesfor a period of 8 days and the appearance of the solutions observeddaily with the results as shown.

polyethylene glycols having an average molecular weight of between 200and 1250.

TABLE I DAYS Monoethanol- 1 2 3 4 5 6 7 8 amino NaOH Ex (parts) (parts)Condition of samples after storage at 2-4 degrees 0 25.8 Semi-solidGel-like Gel-like Gel-like Gel-like Gel-like solid. solid. solid. solid.solid! 0 25.4 Mgkyland do. do. "do? do. D0! ur 0 26.2 Clear and Hazy and..(1o.' .do. do! d0. D0.2

fluid. fluid. 11.8 18.6 do Clear and Clear and Clear and Clear and Clearand Clear and Clear and fluid. fluid. fluid. fluid. fluid. fluid. fluid.14.3 d .do Do. 1&4 ,do do dn dn Do. 18.4 dn rin dn Jin DO, 10.2 do o..do o ..d0 do "do..." Do.

1 Difiicultly pourable.

1 N on-ponrable.

As will be apparent from the foregoing examples, 2. An aqueous detergentcomposition as claimed in the compositions of the present inventioncontaining a claim 1 wherein the linear higher alkyl substituent isselected :mixture of sodium and monoethanolamine salts a mixture ofstraight chain hydrocarbons containing 10 of linear alkylbenzenesulfonic acids exhibit substantialto 13 carbon atoms and the lower alkylsubstituent is 1y improved low temperature stability, remaining clearmethyl. and fluid even after storage for 8 days at temperatures 3. Anaqueous detergent composition as claimed in of 2-4 degrees centigrade.claim 1 wherein the mol ratio of higher to lower alkyl- It will beapparent to those skilled in the art that benzene sulfonic acids isbetween about 3. 0 and 3.5 and many variations and modifications of the'invention as the mol ratio of ethanolamine to sodium cations isbehereinabove set forth, may be made without departing tween about 0.3to 0.7. from the spirit and scope of the invention. The inven- 4. Anaqueous detergent composition according to tion is not limited to thosedetails and applications declaim 2 wherein the lower alkylbenzenesulfonic acid scribed except as set forth in the appended claims. istoluene-benzenesulfonate and the polyethylene glycol W l i has anaverage molecular weight of about 400.

1. An aqueous detergent composition having improved low temperaturestability consisting essentially of as r References Cited solutestherein, in percent by weight of the aqueous com- UNITED STATES PATENTSposition, (A) between about 30 and 50 percent of sodium 3 140 261 7/1964Noad 252 161 and monoethanolamine salts of a mixture of linear 31749353/1965 Eccles 'g 252 161 a s hlgher alkylbenzene sulfomc acld whereinthe alkyl sub- 3,232,852 11/1966 Trusler et a1 stituent is a straightchain hydrocarbon of 9 to 15 car- 40 3 303 13 2 19 7 Dewitt et ah 252137 bon atoms, inclusive, and a lower alkylbenzene sulfonic 3,440,171 319 9 warren 5 acid containing 1 to 6 non-aromatic carbon atoms,inclusive, the mol ratio of higher to lower alkylbenzene LEON ROSDOL, Prm ry Examiner sulfonic acids being between about 4.0 and 2.5 and theWILLIS, Assistant Examiner mol ratio of monoethanolamine to sodiumcations being between about 0.1 and 1.0, and (B) between about 0.5 and 5percent of a polyethylene glycol or mixture of US. Cl. X.R. 252-526,539, 558

